Telephone transmitter



Oct. 14, 1930. c. pococ ET AL TELEPHONE TRANSMITTER Filed March 6, 1929L. C. POCOCK INVEN 1?. BLACKBURN A 7' TORNEY Patented Oct. 14, 1930UNITED STATES PATENT OFFICE 1 LYNDALL C. POCOCK AND REGINALD BLACKBURN,OF LONDON, ENGLAND, ASSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED,OF NEW YORK, N. 'Y., A GOR- PORATION OF NEW YORK TELEPHONE TRANSMITTERApplication filed March 6, 1929, Serial No. 344,774, and in GreatBritain July 28, 1928, V

This invention relates to telephone transmitters and more particularlyto transmitter mouthpieces of the hygienic type.

An object of the invention is to improve the acoustic properties ofmouthpieces for telephone transmitters.

Various attempts have been made to produce transmitter mouthpieces ofhygienic pattern which comprise a smooth outer surface which can beeasily kept clean. To this end, spherical and other shapes ofmouthpieces have been provided, slots or other shaped passages beingformed in the shell for the purpose of allowing sound waves to enter.

It has been found, however, that owing to the relatively large hollowspace in the interior of such mouthpieces they have very poor acousticproperties. vention therefore aims to provide an im proved form of suchhygienic type of mouthpiece in which the above disadvantages areovercome.

In accordance with the present invention a substantially solidmouthpiece having a smooth outer surface is provided with one or moresound passages therein communicating with a passage which is arranged todirect the sound waves onto the transmitter diaphragm. Preferably thefirst mentioned passages are in the form of slots which communicate witha cylindrical central passage transverse to the slots. The said passageswith the transmitter are preferably proportioned in such a manner as toform a mechanical filter.

According to another feature of the invention means is provided to sealthe jointbetween the central passage in the mouthpiece and thetransmitter proper.

Examples according to the invention are illustrated in the accompanyingdrawing in which Fig. 1 is a sectional diagram illus trating a portionof a handset with a spherical mouthpiece. Fig. 2 is a sectional diagramillustrating a modified form of mouthpiece. Fig. 3 is a face projectionof the mouthpiece shown in Fig. 2, and Fig. 4 is a transverse sectionshowing the arrangement of the slots.

It will be seen from the drawing that the The present in-' mouthpieceaccording to this invention com-= prises a substantially soliddome-shaped moulding 1, having a smooth outer surface broken only by theslots 2 which commimicate with a central passage 3 which is arranged todirect the sound waves from the slots onto the transmitter diaphragm.

The cross-sectional area of the slots 2 is arranged to be substantiallyequal to the cross-sectional area of the central passage 3 and in orderthat the junction betweenthe said slots and passage may be effectivewithout any throttling action it will be noted that the outer edges ofthese slots are carried down and converge into the central passage in astepped formation. I

The central passage preferably makes a sound tight joint with thetransmitter proper and for this purpose suitable washers may be providedon the lip 4. The central passage 8 may be cylindrical or slightlyconical the transmitter 9, the floating diaphragm 10 being arrangedbehind the plate and form-. ing the driving member for the granules inthe chamber 11.

It will be seen that with the construction herein described a mouthpieceof very simple form and one which may be readily moulded, is obtained.Moreover, the mouthpiece possesses considerable strength and is ofi1nproved acoustic properties owing to the absence of large hollowspaces within it.

What is claimed is:

1. A transmitter comprising a casing, a diaphragm within said casing,and a substantially solid dome-like mouthpiece attached to said casing,said mouthpiece having long narrow sound passages therein communicatingwith a central cylindrlcal passage arranged to direct sound waves ontosaid dlaphragm.

. 2. A transmitter comprising a casing, a diaphragm Within said casing,and a substantially solid dome-like mouthpiece attached 7 to saidcasing, said mouthpiece having sound 5 passagesthereincommunicating with'a central passage, said sound passages being -in theform of slots whichenter the central pasisage substantially at right angles. A transmitteraccording to claim 2 in 10 which the cross-sectional area of the slotsis substantially equal to the cross-sectional area of the centralpassage, the junction between I v said slots and passage being efiectedWithout ammusgr LA transmitter comprising a casing, a d iaap'hragmWithin said casing, a substantially solid dome-like mouthpiece attachedto said I easing and having a central passage therein, and aise alingmember between 'said in'outhpiece and said diaphragm adjacent saidcentral passage h 5- 5,;A tifansinitter comprising a easing, a;l-i'aphra-gm Within said casing, a substantiallysolid dome-likemouthpiece attached to. said casing having a central passage therein, aniapertured plate between said diaphragm and mouthpiece, and a sealingmember car- Tied by saidfmouthpieceand engaging said pe pre m fiei i '6.A transmitter comprising a easing, a diaphragm within said casing, asubstantially sOliddOIfie-like mouthpiece attached to said casin'gjsaidmouthpiece having sound pas- E'sage's therein communicating with acentral 3%, :pas sagegand a hollow gauze lining in'said central passageoii said mouthpiece.

lo- A transmittercomprising a casing, a diaphragm yv'i'thin said casing,a substantially fsolid dorne-like mouthpiece attached to said 4n casingand having sound passages therein communicating with a centralp'assage,."aiid .a gauze lining in said centr al passage, said flijninghaving an outwardly extending rim held between said mouthpiece and "saiddia- EPhI' g i-HL. .Q 1 P 8 A transmittercomprising a casing, 'adiaghragiri jwithin said casing,iasubstantially o "solid dome-likemouthpiece attachedto said casing haying a central passage thereinfan m:apertured plate between said diaphragm and uth'piece, and Y a sealingring clamped besaid meuthpiece and said ap'erture'd plate. i I j 19.,Atransmitter comprising; a casing, a

diaphragm yvithin'said casing, a substantially solid dome likemouthpiece attached to said casing, said mouthpiece having slits therein7 communicating with a central passage, and a'Ycyl-indnical gauze liningin said central 7 my Qpaissage of said mouthpiece.

' IIAWlfiiQSiS whereof, We hereunto subscribe :QHIflQmGSt-hIS 6th day ofFebruary, 1929,

REGINALD BLACKBURN.-

